Add comprehensive GitHub Copilot instructions for eslint-plugin-primer-react with Node.js v20 support

.github/copilot-instructions.md

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+# eslint-plugin-primer-react
+
+ESLint plugin for Primer React components. This is a JavaScript-based ESLint plugin that provides rules for validating and auto-fixing Primer React component usage.
+
+**Always reference these instructions first and fallback to search or bash commands only when you encounter unexpected information that does not match the info here.**
+
+## Working Effectively
+
+### Bootstrap and Setup
+
+- Install Node.js v20+ (v20 is the current standard):
+  - Check version: `node --version && npm --version`
+- Install dependencies: `npm ci` -- takes 60 seconds. Set timeout to 90+ seconds.
+- **NO BUILD STEP REQUIRED** - This is a direct JavaScript project with main entry at `src/index.js`
+
+### Development Commands
+
+- Run tests: `npm test` -- takes 5 seconds. Fast, no long timeout needed.
+- Run linting: `npm run lint` -- takes 1.5 seconds. Very fast.
+- Run markdown linting: `npm run lint:md` -- takes under 1 second. Very fast.
+- Check formatting: `npm run format:check` -- takes 0.5 seconds. Very fast.
+- Fix formatting: `npm run format` -- applies Prettier formatting fixes.
+
+### Testing and Validation
+
+- **ALWAYS** run `npm test` after making changes to rules - tests run in 5 seconds
+- **ALWAYS** run `npm run lint && npm run lint:md` before committing - both complete in under 3 seconds total
+- **ALWAYS** run `npm run format:check` to verify formatting - completes in 0.5 seconds
+- All validation commands are very fast - no need for long timeouts or cancellation warnings
+
+### Manual Rule Testing
+
+You can manually test individual rules using this pattern:
+
+```bash
+node -e "
+const rule = require('./src/rules/RULE_NAME');
+const {RuleTester} = require('eslint');
+const ruleTester = new RuleTester({
+  parserOptions: {
+    ecmaVersion: 'latest',
+    sourceType: 'module',
+    ecmaFeatures: { jsx: true }
+  }
+});
+ruleTester.run('test', rule, {
+  valid: [{ code: 'VALID_CODE_HERE' }],
+  invalid: [{ code: 'INVALID_CODE_HERE', errors: [{ messageId: 'MESSAGE_ID' }] }]
+});
+"
+```
+
+## Repository Structure and Navigation
+
+### Key Directories
+
+- `src/rules/` - ESLint rule implementations
+- `src/rules/__tests__/` - Jest tests for each rule using ESLint RuleTester
+- `docs/rules/` - Markdown documentation for each rule
+- `src/configs/` - ESLint configuration presets (e.g., recommended.js)
+- `src/utils/` - Utility functions shared across rules
+- `.github/workflows/` - CI pipeline definitions
+
+### Important Files
+
+- `src/index.js` - Main entry point, exports all rules and configs
+- `package.json` - Scripts and dependencies (no build scripts needed)
+- `jest.config.js` - Jest test configuration
+- `.eslintrc.js` - ESLint configuration for the project itself
+- `.nvmrc` - Node.js version specification (v20)
+
+### Rule Development Pattern
+
+Each rule follows this structure:
+
+1. Rule implementation: `src/rules/rule-name.js`
+2. Test file: `src/rules/__tests__/rule-name.test.js`
+3. Documentation: `docs/rules/rule-name.md`
+4. Export from: `src/index.js` (add to rules object)
+5. Optional: Add to `src/configs/recommended.js` if should be in recommended preset
+
+## Validation Scenarios
+
+### After Making Rule Changes
+
+1. Run the rule's specific test: `npm test -- --testNamePattern="rule-name"`
+2. Run all tests: `npm test` (5 seconds)
+3. Test the rule manually using the Node.js snippet pattern above
+4. Verify the rule is exported properly from `src/index.js`
+
+### Before Committing
+
+1. `npm run lint` - JavaScript linting (1.5 seconds)
+2. `npm run lint:md` - Markdown linting (<1 second)
+3. `npm run format:check` - Formatting validation (0.5 seconds)
+4. `npm test` - Full test suite (5 seconds)
+
+### Testing Plugin Integration
+
+The plugin can be tested by:
+
+1. Using manual Node.js rule testing (shown above)
+2. Running existing test suite which validates all rules
+3. Creating test files and using ESLint RuleTester in the **tests** files
+
+## Common Development Tasks
+
+### Adding a New Rule
+
+1. Create rule implementation: `src/rules/new-rule-name.js`
+2. Create test file: `src/rules/__tests__/new-rule-name.test.js`
+3. Add to exports in `src/index.js`
+4. Create documentation: `docs/rules/new-rule-name.md`
+5. Optionally add to `src/configs/recommended.js`
+6. Run tests: `npm test`
+7. Run linting: `npm run lint`
+
+### Modifying Existing Rules
+
+1. Edit rule in `src/rules/rule-name.js`
+2. Update tests in `src/rules/__tests__/rule-name.test.js`
+3. Update documentation in `docs/rules/rule-name.md` if needed
+4. Run tests: `npm test`
+5. Test manually using Node.js snippet if needed
+
+### Working with Changesets (for releases)
+
+- `npx changeset` - Create a changeset for changes
+- `npx changeset status` - Check changeset status
+- Changesets are used for versioning and publishing to npm
+
+## Troubleshooting
+
+### Common Issues
+
+- **Node.js version**: Use Node.js v20+ (v20 is the current standard)
+- **Dependencies**: Always use `npm ci` instead of `npm install` for consistent installs
+- **Test failures**: Run `npm test` to see specific failures - tests are fast and detailed
+- **Lint failures**: Run `npm run lint` and `npm run lint:md` to see specific issues
+- **Format issues**: Run `npm run format` to auto-fix formatting
+
+### Rule Testing Issues
+
+- Use the RuleTester pattern shown above for manual testing
+- Check that messageId in tests matches the rule's meta.messages
+- Verify JSX parsing works by including ecmaFeatures.jsx in parserOptions
+
+## Command Reference
+
+Essential commands and their typical execution times:
+
+- `npm ci` - Install dependencies (60 seconds)
+- `npm test` - Run all tests (5 seconds)
+- `npm run lint` - Lint JavaScript (1.5 seconds)
+- `npm run lint:md` - Lint Markdown (<1 second)
+- `npm run format:check` - Check formatting (0.5 seconds)
+- `npm run format` - Fix formatting (similar time)
+
+All commands except `npm ci` are very fast. No need for extended timeouts or cancellation warnings on validation commands.